My 3901 makes almost zero transmission whine when using Low Range during operation. (loader work, back blading, landscape rake). When I put it in Medium Range, noise gets a little louder, and in High Range it's quite loud. Maybe a range selection change to a lower range would reduce your noise level. The whine is inherent in Hydrostatic transmissions, but will likely reduce after the first transmission oil/ filter change. Some are just noisier than others. Use the recommended Kubota oil and dont skimp by buying cheaper stuff. Using cheaper stuff with cost you 1000x more than you saved in the long run.